The threat of a nuclear-armed Iran is emerging as the most high-profile foreign policy issue on the Republican presidential campaign trail.

The GOP candidates agree the world would be more dangerous if Iran obtains nuclear weapons. But there are differences over how to prevent the Islamic republic from acquiring a nuclear bomb, especially on whether the emphasis should be on military force, or if diplomacy and economic sanctions should be the main focus.

“In the short term, Iran is likely to be at the epicenter of any crisis the next president faces; the next 3 a.m. phone call,” said Iran expert Michael Rubin, a senior lecturer at the Naval Postgraduate School and a resident scholar at the American Enterprise Institute.

Matt Powell, 38, a rock quarry manager from Cedar Rapids who is weighing his support for several Republican presidential candidates in the Iowa caucus campaign, said he’s convinced diplomacy and sanctions won’t persuade Iran to halt its nuclear development program. He believes military action will ultimately be needed, although he wouldn’t be opposed to “just getting out of Israel’s way and letting them do it.”

A report issued in November by the International Atomic Energy Agency pushed Iran’s intentions to the forefront, citing “credible” evidence Tehran may be developing a nuclear weapon.

Those findings have stoked a debate within the United States, Israel and other countries over whether a military strike should be employed to destroy Iran’s nuclear facilities if other measures don’t succeed.

Iran has warned it will respond to any attack by attacking Israel, its arch-enemy, and U.S. interests in the Persian Gulf region.

President Barack Obama’s administration has said the policies of the United States and the international community have succeeded in increasing pressure on Iran, which has resulted in its global isolation.

In a speech last month at the Brookings Institution in Washington, National Security Adviser Tom Donilon said Obama has always been clear that Iran’s nuclear program is a grave threat to global security and that the United States is not taking “any options off the table in pursuit of our basic objective.”

Former U.S. Sen. Rick Santorum, a hawk on Middle East policy, told a town hall meeting in Anamosa last month it’s inevitable that Israel will strike Iran in an effort to destroy its nuclear development facilities. He said the United States should ensure Israel succeeds.

While other countries already have nuclear arms, Santorum said Iran would be the most dangerous because it is a “radical Islamist theocracy” bent on taking over the world for Islam.

He also proposed other steps to “stop Iranian nuclear aggression,” including sanctions on Iran’s central bank and helping pro-democracy groups within Iran.

Former Massachusetts Gov. Mitt Romney also takes a hard-line stance, saying he would not allow Iran to have a nuclear weapon. In his first 100 days in the White House, Romney said he would make it clear the military option is on the table by ordering the regular presence of aircraft carrier task forces in both the Eastern Mediterranean and the Persian Gulf region.

Romney said in a policy paper he would also begin talks with Israel to increase military coordination and impose tougher sanctions on Iran.

Even former Ambassador Jon Huntsman, a moderate on many issues, said he couldn’t live with a nuclear-armed Iran. “If you want an example of when I would use American force, it would be that,” he said in a speech in October at Southern New Hampshire University.

Meanwhile, Texas Gov. Rick Perry said he would support an Israeli airstrike on Iran if there is proof Tehran is moving closer to having a nuclear weapon. “Obviously, we are going to support Israel,” he told CNN.

Mark Finkelstein, director of community relations for the Jewish Federation of Greater Des Moines, said he sees five or six options for dealing with Iran. But a U.S. military response has to be available “because without it there is really no teeth to any of the other possibilities,” he added.

Not everyone agrees with such a hard-edged stance.

U.S. Rep. Ron Paul said the last thing he wants is an Iran with a nuclear weapon. But he also warns Americans not to overreact.

“When I was in the military, we stared down the Soviet Union and their 35,000 nuclear weapons with strength and diplomacy — not war,” Paul said. “As former Defense Secretary Robert Gates has pointed out, our national debt is the greatest threat to this country’s national security. And I believe spending trillions more on war with Iran — as we’ve done in Iraq and Afghanistan — would be a huge mistake and would further damage our economy and national security.”

Ervand Abrahamian, a native of Iran and a professor at City University of New York, said there is general misperception in the U.S. that Iran is determined to obtain a nuclear weapon.

He believes Iran’s leaders simply want the capability to make a bomb if they ever need it to protect their country, which is a subtle, but important difference, he said.

It’s important to recognize the formative political thinking for Iranian leaders occurred during the Iran-Iraq war in the 1980s, when Iraq used chemical weapons of mass destruction against Iran, Abrahamian said.

Jeffrey Weiss, director of the Catholic Peace Ministry in Des Moines and a leader of Iowans for Diplomacy with Iran, urges against a rush to judgment against Iran. He also suggests a military strike on Iran would only cause the Islamic republic to accelerate the weaponizing of its nuclear program. He favors “serious regional diplomacy.”

Former House Speaker Newt Gingrich offers another approach. He said in a CBS/National Journal debate he favors covert operations in Iran that include “taking out their scientists” and breaking up their systems — a tactic some experts believe is already being used.

Gingrich also said the United States should also maximize its coordination with the Israelis and have a strategic program employing every possible tactic short of war to bring down the Iranian regime.

“If, in the end, despite all those things, the dictatorship persists, you have to take whatever steps are necessary to break its capacity to have a nuclear weapon,” Gingrich said.

U.S. Rep. Michele Bachmann told The Des Moines Register’s editorial board in November that Iran needs a signal from the United States that it has something to lose if it continues to go forward with a nuclear weapons program.

“They have continued to develop not only the enriched uranium but also the ability to deliver a nuclear weapon,” Bachman said. She has vowed she would never allow Iran to obtain nuclear weapons that would threaten Israel and the United States.

Question: What would be your administration’s position on the war in Afghanistan?

President Barack Obama has elevated his advisers to the rank of general and is waging the nation’s wars from his 2012 campaign headquarters in Chicago, Bachmann said in a November meeting with The Des Moines Register’s editorial board. By withdrawing U.S. troops from Iraq this year and announcing he will do the same in Afghanistan in late 2012, Obama has put political considerations ahead of the country’s national security interests, she said. The congresswoman has argued the U.S. needs to “stay the course” and “finish the job” in Afghanistan and she has praised progress made by U.S. troops there.

Gingrich has opposed Obama’s withdrawal plans because he believes it is “signaling to the world we are getting out.” But he has not been optimistic about the Afghan war while campaigning in Iowa, saying it “is not going to end well.” He has suggested the counterinsurgency doctrine created by Gen. David Petraeus “doesn’t go deep enough for some place like Afghanistan.” He added, “You’re dealing with Afghan culture that is fundamentally different than us, in ways we don’t understand.”

Huntsman favors a pullout of U.S. troops in Afghanistan and he has called for speeding up the timetable established by Obama because of the war’s cost and dwindling public support. “When you look at Afghanistan, can we hang out until 2014 and beyond? You can, if you’re willing to pay another quarter of a trillion dollars to do so,” he told the Associated Press.

“Defending our nation is the most important responsibility of the federal government,” Paul said. “That’s why after the horrific 9/11 attacks, I voted to authorize military force to hunt down Osama bin Laden, and I also authored legislation to specifically target terrorist leaders and bring them to justice. Today, however, hundreds of thousands of our fighting men and women have been stretched thin all across the globe in over 135 countries — often without a clear mission, any sense of what defines victory, or the knowledge of when they’ll be permanently reunited with their families. Acting as the world’s policeman and nation-building weakens our country, puts our troops in harm’s way, and sends precious resources to other nations in the midst of an historic economic crisis. Taxpayers are forced to spend billions of dollars each year to protect the borders of other countries, while Washington refuses to deal with our own border security needs. The mission has been accomplished in Afghanistan, and it’s time to come home and return to a foreign policy that put America’s security first.”

Perry said in a statement that he “wants to bring our brave men and women home as soon as we safely can, based on the advice of military commanders on the ground and after consulting with our allies, including the Afghan leadership.” But he also believes keeping Afghanistan free from a terrorist-supporting regime “remains as vital a strategic interest for the United States today as it was 10 years ago.”

Romney said in a policy paper that the nation’s objective in Afghanistan should be to ensure the country “will never again become a launching pad for terror.” He has said that in his first 100 days as president, he would order a “full interagency review of our transition in Afghanistan.” He would also review military and assistance presence to determine the level required to secure our gains and to train Afghan forces to the point where they can protect the sovereignty of Afghanistan on their own. Withdrawal of U.S. forces from Afghanistan under a Romney administration would be based on conditions on the ground as assessed by our military commanders, Romney said.

Santorum has criticized Obama’s plan to withdraw troops from Afghanistan, objecting to the administration setting limits on time and resources in the war effort. “Every American wants our brave men and women home safely, but we cannot let those who’ve given the last full measure die in vain by abandoning the gains we’ve made thus far. We must be squarely focused on succeeding in Afghanistan rather than on politically motivated troop withdrawals,” he said in a June campaign news release.